Maryland Gov. Martin O'Malley (AP Photo/Patrick Semansky)

Aides to O’Malley said they were told the decision came after the NBC talk show scored an interview with Jamie Dimon, the chief executive of JPMorgan Chase, which announced a staggering $2 billion trading loss this week.

O’Malley, who has become a regular on the Sunday talk-show circuit since ascending to chairman of the Democratic Governors Association, was booked to discuss same-sex marriage and the 2012 campaign.

O’Malley signed Maryland’s same-sex marriage law in March. It is expected to be petitioned to the ballot in November. The governor has been a staunch defender of President Obama, who announced his support of gay nuptials this week.